While a typical radar beam is adequate for locating a target in an early warning role, it is generally not accurate enough for aiming a radar antenna to track the moving direction of the target. In some applications, the beam width of the radar beam can be reduced through the use of a larger antenna, but this is not often practical, for example, in airborne radar applications. One way to improve the performance of the radar is through monopulse processing.
In a typical monopulse radar, a radar beam is sent out of an antenna array, and the reflected signals of the radar beams are received separately in slightly different return paths, causing a difference in received phase. The received phase of the two returns are compared to each other, indicating the position of the reflecting target within the received beam. Thus, the general direction of the target relative to the boresight of the antenna can be determined during one pulse. In order to perform monopulse, an antenna is functionally split into two parts (antenna A and antenna B) that receive the reflected radar beams off the target at slightly different angles. In monopulse antennas generally known in the art, two outputs are created from the antennas A and B. One output is the sum of parts (A+B), and another output is the difference of parts (A−B). The sum and difference outputs are processed by a suitable processor (e.g., a computer, microprocessor, etc.) according to generally known monopulse processes to determine the position of the target. Generally, monopulse techniques can resolve target position to about one tenth of the beamwidth of the radar beams.